Continous reboots with Guru Meditation Error

[pvdzee]

The watch gets in a continuous boot loop. After the "cyberWatch starting" message on Serial Monitor the watch reboots with serial monitor message "guru meditation error: core 1 panic'ed (cache disabled but cached memory region accessed)".
See full message below:

cyberWatch starting
Guru Meditation Error: Core 1 panic'ed (Cache disabled but cached memory region accessed)
Core 1 register dump:
PC : 0x400d4a4c PS : 0x00060034 A0 : 0x80082018 A1 : 0x3ffbff40
A2 : 0x3ffbdcf0 A3 : 0x20000000 A4 : 0x00000400 A5 : 0x3ffb19a0
A6 : 0x00000000 A7 : 0x3ffb19dc A8 : 0x80081419 A9 : 0x00000000
A10 : 0x00000000 A11 : 0x3ffb1b20 A12 : 0x00000000 A13 : 0x3ffb1980
A14 : 0x00000000 A15 : 0x00000005 SAR : 0x0000001d EXCCAUSE: 0x00000007
EXCVADDR: 0x00000000 LBEG : 0x4008cabc LEND : 0x4008cad8 LCOUNT : 0x00000000
Core 1 was running in ISR context:
EPC1 : 0x4009589f EPC2 : 0x00000000 EPC3 : 0x00000000 EPC4 : 0x400d4a4c

ELF file SHA256: 0000000000000000

Backtrace: 0x400d4a4c:0x3ffbff40 0x40082015:0x3ffbff60 0x4008a809:0x3ffbff80 0x4009589c:0x3ffb1a00 0x400960b9:0x3ffb1a20 0x4008b70c:0x3ffb1a40 0x40154137:0x3ffb1ab0 0x40122d1e:0x3ffb1ae0 0x40122f3a:0x3ffb1b10 0x401243d7:0x3ffb1b40 0x40125db9:0x3ffb1b80 0x401227d6:0x3ffb1bc0 0x40121580:0x3ffb1bf0 0x40145f71:0x3ffb1c50 0x4000bcc5:0x3ffb1c70 0x4017a579:0x3ffb1c90 0x40175e90:0x3ffb1cb0 0x400d9072:0x3ffb1d30 0x400d19b6:0x3ffb1d60 0x400d1c4f:0x3ffb1df0 0x400d1c6b:0x3ffb1e10 0x400d167f:0x3ffb1e30 0x4017df75:0x3ffb1e70 0x400d4199:0x3ffb1e90 0x400d41a5:0x3ffb1ec0 0x400d44a2:0x3ffb1ef0 0x400d4730:0x3ffb1f50 0x4017df23:0x3ffb1f70 0x400d8b45:0x3ffb1f90 0x400e2c59:0x3ffb1fb0 0x4008fcde:0x3ffb1fd0

Rebooting...
cyberWatch starting

Any idea what could cause this problem?